Method of and apparatus for stabilizing a vehicle in slow rotation,along a fixed direction



DO MAU L ARATUS FOR Apnl 8, 1969 AM 3,437,288

METHOD OF AND APP STABILIZING A VEHICLE n1 snow ao'm'rzon. ALONG A FIXED DIRECTION F11 Sept. 20. 1966 Sheet 1 Of 7 April 8, 1969 DO MAU LAM 3,437,288 IETHQD OF AND APPARATUS FOR STABILIZING A VEHICLE IN SLOW ROTATION, ALONG A FIXED DIRECTION Filed Sept. 20, 1966 Sheet 2 of 7 F/azb April 1969 I be MA u LAM I 3,437,288

lB'l'l-IOD OF AND APPARATUS FOR STABILIZING A VEHICLE IN SLOW ROTATION. ALONG A FIXED DIRECTION rmd se z. 20. 1966 Sheet 3 or 1 FIG.4 o

P 8 1969 no MAU LAM 3,437,288-

METHOD OF AND APPARATUS FOR STABILIZING A VEHICLE IN SLOW ROTATION, ALONG A FIXED DIRECTION 4 Filed Sept. 20, 1966 Sheet or 7 qoz 1'02 (1'03 .p'oa H I F F 1 '3 l '5 t I ll Ill j 1 2 a 4 s "a s c I all I'm dOZ ['02 I z z z 2 DO MAU LAM Apnl 8, 1969 3,437,288 I us'raon or AND APPARATUS FOR STABILIZING A VEHICLE IN sLow ROTATION, ALONG A FIXED nnmcnon P11! 509%. 20, 1966 Sheet 5 or? .n p m 1 h f 2 Q a S 8 I "cl! 0 I Z vm Am S h M 0 m m 0 d w I b I N N N l O a H n: m a a on u a M c d I b 6 m w w Controls Detector Controls A ril 8, 1969 DO MAU LAM 3,437,288

METHOD OF AND APPARATUS FOR STABILIZING A VEHICLE IN SLOW ROTATION, ALONG A FIXED DIRECTION Filed Sept. 20. 1966 Sheet 6 or 7 Trigger 11; 10a Rovors'mq h Davic/ 1 1 Mocsurmq 11b 10b Dwico 8b 3b 9b vulva 11b III: R Reversing 1 5b Device Adder 1311 g Trigger Sequence 7 [Clock p 1969 no MAU LAM 3 METHOD OF AND APPARATUS FOR STABILIZING A VEHICLE IN SLOW ROTATION, ALONG A FIXED DIRECTION Filadsept. 20. 1966 Sheet of 7 tmmfim' mm) Mm) tn +1 1 I F h I I l 1! 1 iv l f f2 l a ll United States Patent i 3 437,288 METHOD OF AND APIARATUS FOR STABILIZING A VEHICLE IN SLOW ROTATION, ALONG A FIXED DIRECTION Do Mau Lam, Paris, France, assignor to Nord-Aviatlon Societe Nationale de Constructions, Aeronautiques, Paris, France, a joint-stock company of France Filed Sept. 20, 1966, Ser. No. 580,642 Claims priority, application France, Nov. 13, 1965, 38,275, Patent 1,468,913 Int. Cl. G06f /50; F42b 15/02 U.S. Cl. 244--3.15 9 Claims ABSTRACT OF THE DISCLOSURE A method and device for stabilization of a vehicle rotating at slow speed wherein the method includes a timecounter for when the vehicle is in a favorable spatial position for stabilization, measurement in relation to a set of axes and of applying correcting couples. The device includes a detector for comparison to orthogonal axes, a sequence clock, sampling device, with a converter for transforming detector indications to torque impulses with. means for applying the impulses for stabilization.

The present invention relates in the first place to a method for stabilizing, along a fixed direction, in the shortest possible time and with the lowest possible expenditure of energy, any aerial vehicle rotating at a constant slow speed about its centre of gravity, the axis of symmetry of which is coincident with one of the principal axes of its ellipsoid of inertia, of which two moments of inertia are equal to each other, in which the angle formed by the axis of symmetry with the fixed direction is less than 10 and which is subjected at the initial instant to a Poinsot movement, that is to say such that all the external couples with respect to its centre of gravity are zero.

Prior to the present invention, the means employed to :nsure the stabilization of such a vehicle utilized the wellcnown principle consisting of causing the said vehicle to mate rapidly about its centre of gravity.

If the principal moments of inertia of the vehicle are 'epresented by A, B and C (A being equal to B because )f the symmetry), each ratio C/A, necessarily comprised etween l and 2, governs, when the rotation is slow, the :eriod between characteristic instantaneous positions of a nobile axis with respect to a fixed or given reference axis t which the vehicle to be stabilized is found under con- Iitions favourable to its stabilization. Apart from the ingle remarkable case for which C/A =1.5, at which one f these characteristic instantaneous positions is encounared at each period of rotation of the vehicle, all the ther characteristic instantaneous positions, for all other ossible ratios of C/A, will only occur at periods differnt from the exact period of rotation of the vehicle to be Iabilized.

In consequence, the method according to the invention essentially characterized by the fact that it consists, for ll the ratios C/A:

Of defining by means of a-time-counter, uniformly disibuted characteristic instantaneous positions, for each E which the vehicle to be stabilized is found in a spatial Jsition favourable to its stabilization;

Of measuring by means of a detector and at each char- :teristic instantaneous position, the position of the fixed abilization direction with respect to the geometric axis f the vehicle to be stabilized;

And of applying to the vehicle, at the characteristic in antaneous position defined above, correcting couples,

3,437,288 Patented Apr. 8, 1969 in which T is the period of rotation of the vehicle and A and C respectively one of the first twoand the third moment of inertia of the vehicle.

The invention also relates to a device for carrying into effect the method specified above, this device being essentially characterized by the fact that it comprises, in combination:

A detector of the differences between the fixed direction and the geometric axis of the vehicle defining a plane perpendicular to the axis of rotation of the vehicle, the said differences being expressed by director cosines;

A sequence clock supplying the characteristic instantaneous positions of switching defined from the structural shape of the vehicle;

A sampling device controlling, on the one hand the storage in a memory of the indications of the detector at each of the characteristic switching instantaneous positions, and on the other hand, the reading of these stored indications at each of the characteristic switching instantaneous positions immediately following that of the detection, and finally, after a very short lapse of time, the de-sensitizing of the said memory;

A converter transforming the indications of the detector on the director cosines into torque impulses;

And means for applying the said impulses to the axis of the system of the vehicle to be stabilized.

Other characteristic features, advantages and particularities of the present invention will be brought out in the description which follows below, reference being made to the accompanying drawings, in which:

FIG. 1 is a geometrical diagram of the geometric axis of the vehicle with respect to the system of fixed or given reference axis;

FIGS. 2a and 2b are diagrams showing the relative rolling movement illustrating the concept of FIG. 1;

FIG. 3 is a diagram showing the action of the applied torques relating to the concept of FIG. 1;

FIG. 4 is a diagram showing the confirmation of the two systems of axis in a characteristic instantaneous position;

FIG. 5 is a diagram showing the manner in which aiming errors are converted into torque impulses;

FIGS. 6 and 7 are vector diagrams showing the process of stabilization according to the invention; and

FIG. 8 is a diagram which shows on the time axis a cycle of the process of stabilization according to the invention.

FIG. 9 is a synoptic diagram showing one possible form of construction of an assembly of elements enabling the ifnethod according to the invention to be carried into efect;

FIG. 10 is a diagram showing an electronic stabilization circuit for a vehicle, according to a preferred form of embodiment of the invention;

FIG. 11 is a diagram of a stabilization sequence obtained by means of the electronic circuit of FIG. 10;

FIG. 12 is a diagram showing the manner of effecting the detection of the director cosines, together with the arrangement of the gas-jet nozzles on the vehicle to be stabilized, permitting correction couples to be applied to the said vehicle.

In order to make clearly evident the object of the present invention and its essential applications, it appears necessary to explain as clearly and simply as possible the problem set by the stabilization, with respect to a fixed direction, of a free solid in rotation, such as for example an artificial satellite in its orbital movement, or a ballistic device or again a missile in motion on its trajectory.

It s important to note that under steady conditions during which the aiming error with respect to the fixed direction is small, the stabilization must be rapid, fine and accurate, with piloting logistics which only involve a consumption of gas which is as small as possible.

The components to be employed in such a case must be reduced to a minimum and the piloting system must be continuous so that a controlled stabilization is realized wherein a self setting actuation of the process of stabilization occurs as soon as an accidental aiming error takes place.

The method of stabilization according to the invention enables these results to be achieved, as will become clear from the remainder of the present description.

First of all, it should be recalled that the spatial position of a free solid in rotation and subjected to a Poinsot movement can be represented as a solid rotating about an axis variable in space and with respect to the solid, while the resultant of the couples applied at its centre of gravity is zero.

Referring now to FIG. 1, it is seen that if the main orthogonal axes of the said solid are represented by Gx, Gy and Gz, and A, B and C are its principal moments of inertia on the said axes, it being understood that A is equal to B because of symmetry, the ellipsoid of inertia which will characterize the solid will be elongated along Gz if C is less than A; it will be flattened if C is greater than A, and it will become a sphere if C A.

Considering the kinetic moment H of this solid, the components of which are respectively Cr, Ap and Bq, and in which r, p and q are the projections on the axes Gz, Gx and Gy of the instantaneous angular speeds of rotation, it is possible by defining a ratio C/A by way of example to represent the movement of the instantaneous rotation axis G by causing a cone with axis G2 to roll without slip along a cone of axis GI-I or vice-versa, the instantaneous axis of rotation G'y being then constituted in both cases by the line of contact of the generator lines of the two cones, G representing a cone generator line for the identification of the displacements.

In such a representation, it is seen that if the axis Gy moves at an angular speed r about 62, the line 1 taken on the generator line of the cone of axis GH will move around GH at an angular speed 0 such that the ratio between these speeds is given by the relation:

which, for a ratio C/A comprised between 1 and 2, will result in the relation:

If it is sought to stabilize the vehicle thus defined along a fixed direction GS, or more precisely if it is desired to bring into coincidence the axes GH, Gz and GS, assuming that the aiming error represented by the angle 0 is small, that is to say less than 10, it is known from conventional mechanics that the detection of the aiming error and the application of the correcting couples can only be effected when the axis of rotation G2, the kinetic moment of axis GH and the generator G of the cone are located in the same plane, thereby justifying the search for knowledge of the characteristic instantaneous positions at which the said axes are then located in the said plane.

The present invention thus relates to a method which makes it possible to find, when the ratio C/A of the vehicle is known, this being furthermore capable of having any value comprised between 1 and 2, all the character- 4 istic instantaneous positions from the above-cited relation t=TA/ 2C.

The method according to the invention is consequently characterized essentially by a sequence of operations consisting:

(1) Of defining by means of a time-counter of any appropriate type, uniformly distributed characteristic instantaneous positions at which the solid to be stabilized Will be found in a position favorable to the measurement of the aiming error and to the application of the correction couples;

(2) Of obtaining by means of a detector of any suitable type, and at each characteristic instantaneous position, the position of the fixed stabilization direction with respect to the system of axes coupled to the solid to be stabilized.

(3) Of applying to the solid, at the characteristic instantaneous positions defined a bove, correction couples, the value of which at a given characteristic instantaneous position is directly derived from the measurement effected at the characteristic instantaneous position 'which has immediately preceded it.

More particularly, the invention also relates to the means Which can be employed in defining the characteristic instantaneous positions, together with the manner of defining the method of application of correction couples so as to obtain the most rapid possible duration of stabilization.

In order to give an idea of the geometric representation of the movement of the vehicle to be stabilized, there has been chosen in FIGS. 1, 2a and 2b, purely by way of explanation and Without any limitation, a case in which C and. A are in simple ratio which can easily be shown, namely C/A=8/5.

In such a case, the time interval which separates two consecutive characteristic instantaneous positions is, for one revolution of the solid;

or one characteristic instantaneous position every 0.3125 part of a revolution or 3.2. characteristic instantaneous positions per one revolution.

In FIGS. 2a and 2b which give an idea of the relative rolling movement analysed in the plane P1 of FIG. 1 it is seen that if the circumference representing C is considered as fixed and the circumference which represent: A (the case of FIG. 2a) is considered as mobile from ar initial instant t at which the point z, H and p are in alignment, 7 being the tangential joint of the two circumfer ences at a speed 82 and r and p a point coupled to the mov ing circumference at a speed 9, the hypocycloid of p i. such that the alignment of the three points z, H and p i again reproduced at 2. m, H at the instantaneous posi tion t at z, H, p at the instantaneous position at 2 Pa, H' at the instantaneous position t etc; t t t being thus truly the characteristic instantaneou positions desired.

A similar reasoning which provides an identical resul can be made by considering the circumference A as fixel and the circumference C as mobile. FIG. 2 gives an ide of this equivalence.

It can immediately be seen that these successive mc ments of alignment are spaced apart by t=TA/2C i which T is the known period of rotation of the vehicl to be stabilized. It follows furthermore from a study 0 FIG. 1, that the analysis of the movement of the axe can be made by an observer or by an appropriate meat uring or detection apparatus, coupled to the solid, th said observer looking at the movement of the vector joining together the points of intersection of the said axe with a plane P assumed to be fixed, which is perpendict lar to the axis Gz and has a dimension GO=1 with It spect to the centre of gravity G of the solid. In this even the result is that S is the intersection of GS with P 0 5 that of G7 and H that of GH with the same plane P while the respective positions of these points in the same plane Gx, Gy is given by their respective projections.

Thus, P, Q are the director cosines of the direction of the kinetic movement GH; p, q, the components of the direction of the instantaneous axis of rotation G7; and a'fi' are the director cosines of the fixed direction GS with respect to the system of axes G, x, y displaced by an angle 1rA/C with respect to the system G, X, Y, for reasons which will be explained later.

In the example given above, the ratio C/A has been chosen in such manner that the characteristic instantaneous positions are repeated every of the period of rotation of the solid.

It will be shown in the portion of the description which follows how it is possible to design a process tending to stabilize the solid at each of the characteristic instantaneous positions and this equally well for the particular ratio or C/A taken by way of example in the case of FIGS. 1, 2a and 2b as for any other ratio of C/A comprised between 1 and 2, that is to say, as has previously been seen, for any ratio of C/A for which we have the relation:

There will also be shown the manner of determining the value of the correction couples to be applied to the solid at each of the characteristic instantaneous positions in order to obtain stabilization of the solid in the quickest possble way.

When examining the plane P the observer, who is :oupled to the solid, sees: on the one hand the point S rotating about H at the speed 9, since the length H S .hen remains constant; and on the other hand, the point I-I rotating about 0 at the speed r, since the length GO vhich is by definition equal to unity, obviously remains :onstant.

This movement remains valid as long as the coupled hown diagrammatically in FIG. 1 by the arrows +L .nd -L for the axis Gx and +M and M for the axis Try, are not applied, that is to say as long as L=O and 4:0.

If there are applied (see FIG. 3) on the axes Gx and 5y couples L and M of constant intensity but of very hort duration, the point H in the plane P is seen to love to the position H in such manner that the vector as as components quantities L and M respectively proortional to the duration of the couples L and M applied n the axes Gx and Gy. On the other hand, the point S oes not move and remains at its position S It is seen that the initial configuration of the points H and O which existed before the impulse of the )ITCCIIOII couples and which is shown diagrammatically l full lines in FIG. 3, becomes, after the impulse of the id couples, the configuration S H',,, 0 shown diagramatically in broken lines in the same FIG. 3.

The values of the couples to be applied are derived om the measurement (see FIGS. 1 and 4) of the comments a' and fi' taken from the system of axes Gx, y, which necessitates the displacement of the co-ordiltCS of the detector, with respect to the system of axes x, Gy, by an angle equal to 1rA/C or 360 A/ZC.

If FIG. 4 shows the respective configuration of the sysns of axes x, 0, y and x, 0', y at the characteristic inmtaneous position t that is to say that at which the lues oc' and fl' are obtained, it will readily be underod that if at the characteristic instantaneous position r rich follows immediately, that is to say that values a /2 and B' /Z (see FIG. 5) are converted to )portional couple impulses applied to the axes Gx and Gy, the point H will move to the position H and the configuration will change from O, H S shown in full lines to the configuration O, H' S shown in broken lines.

In order to make a complete demonstration of the process of stabilization according to the invention, the process will be started, referring to FIGS. 6 and 7, from the moment when the stabilization is completed, that is to say from the moment of coincidence of the points 0, H and S, designated respectively at that instantaneous position by 0, H and S in FIG. 6. At the characteristic instantaneous position immediately preceding, we had 0, S H with coincidence of O and S At the instantaneous position before that, we had the configuration 0H such that H was located in the centre of CS and the time interval was such that the time taken by OH to sweep the angle 1 (see FIG. 7) was equal to that taken by HS to sweep the A conventional calculation by the complex numbers, which will not be reproduced here so as not to overload the description uselessly, makes it possible to show that :HzHa is actually a function of and at the instantaneous position Generally, H H bringing back H to the centre of OS, is equal to 08 displaced through an angle 1rA/C.

In FIG. 8, there has been shown on the time axis a cycle of the process of stabilization in accordance with the invention.

In this figure, t t and 1 are the characteristic instantaneous positions separated from each other by an identical interval t=T A /2C which is determined by the shape of the vehicle to be stabilized.

The arrows F F and F represents the moments at which the measurements are effected of the components Ma -H0 a0 ,80 do -5'0 at the respective characteristic instantaneous positions t t and t The arrows F 3Ff3 and F F represent respectively the beginnings and ends of the application of the correction couples to the axes Gx and Gy, which couples are equal to aol/Z and B'ol/Z immediately after the instantaneous position t and to:

a02/2 and 5'02/2 immediately after the instantaneous position t It results from the foregoing that the process of stabilization according to the present invention thus consists;

Of continuously detecting the values of the director cosines in the system of axes x'y;

Of storing these in a memory at switching instantaneous positions separated by constant intervals of time which depend on the structural condition of the solid;

Then of reading them and converting them to torque impulses which are applied at the switching instantaneous position immediately following, along the axes Gy and Gx.

The method according to the invention thus permits, when the ratio C/A is known, of stabilizing in an optimum time all the vehicles subjected to the conditions which have been previously explained. This method provides a good compromise between the energy consumption of the stabilization device, which is very close to the minimum theoretical value, the number of components, which is reduced to a minimum and which remains identically the same both for small and for relatively large aiming errors, and the accuracy of the stabilization which can in fact be very high.

There will now be described with reference to FIGS. 9 to 12, the means enabling the method according to the invention to be carried into eflect.

Reference will first of all be made to the synoptic diagram of FIG. 9 which shows a possible form of construction of a group of elements for carrying out this method, and also to the basic FIGURES 1, 2a and 2b of the invention.

In FIG. 9, 15 represents a detector displaced by 1rA/C mounted on the solid to be stabilized, which gives the difference between the axis of symmetry Gz of the solid and the fixed direction GZ in the form of director cosines on [3' of this direction with respect to the axes Gx and Gy', the angle between the axes Gz and GZ being less than by hypothesis.

A sampling unit 17 which has the three-fold function of controlling: on the one hand by a first series of elements 16a, 16b, 16c and 16d, the storage in memories 18a, 18b, 18c and 18d of the indications of the detector at the characteristic instantaneous positions t,,; on the other hand, by a second series of elements 19a, 19b, 19c and 19d, the reading of these same indications at the instantaneous positions I a-A, and then after a very short time, the desensitizing of the memories at the instantaneous positions t,,-|-7\ A conversion unit, comprising adding devices e and 20 and selectors 21c and 21 transforms the data a',,, fi',,, supplied by the detector 15 to torque impulses du /2 and 6,6,,/ 2.

There has been shown in FIG. 10 a preferred form of embodiment of an electronic stabilization circuit in the case of a non-limitative application of the invention to an artificial satellite having a form of revolution about the axis Gz, this axis being compelled to coincide at every instantaneous position with the direction of the sun GZ, in spite of the apparent movement of the sun and of possible disturbances.

The director cosines or, ,8 of the direction GZ of the sun are continuously detected by means of a conventional device such as a photo-electric cell for example, and electric voltages proportional to the co-orrlinates of these cosines are collected at the output of the measuring device 1. In order to avoid any ambiguity and to facilitate the description, the reference a will be added to everything which concerns the signals produced from the cosine on and the reference b to everything concerning the signals coming from the cosine ,8. These signals are amplified at 2 2 and then applied, through the intermediary of electronic gates 301 3:1 and 3b 3b to memory storage condensers 4a 4a and 4b 4b Diodes Sa and 5b 5b; deliver polarized signals respectively to the trigger circuits 7a 7a and 717 711 in turn connected to adding devices 8a and 812.

A sequence clock 12 has the double function of controlling on the one hand the closure of the gates 3e1 Qui and 3b 3b on the other hand, the operation of the reversing devices 9a and 9b. Each of these reversing units is connected on the downstream side of the respective diodes Sa 5o and 5b 5b through the intermediary of resistances 6e1 6612 and 611 612 The signals deliveredby the adding devices 8a and 8b are converted to torque impulses through the intermediary of selection diodes 11:1 11o and 1112 1112 acting respec- 8 tively on gate-valves 10a 1041 and 10b 10b controlling gas jet nozzles 13a 13a and 1317 1311 In a system of this kind, the ratio of the signals (11' [3) to impulses has been provided in such manner that when the said signals are applied to the valves 10a 10a and 1012 1012 which open the nozzles, the latter produce jets of gas, the impulse of which is equal, in absolute values, to half the value of each signal received. Thus, signals of levels a, and 5' will produce at the nozzles impulses 6 and Will result in corrections equal to a,,/ 2 and ti /2.

Purely by way of explanation, there will be described below with reference to FIGS. 10 and 11 the process of treatment of the signal or alone, comprising its storage in a memory, its reading and then its adaption for application to the impulse members. It is understood that the process relating to the signal [3 is identical with that of the signal a.

At the instantaneous position t the signal a, corresponding to the instantaneous voltage 2 e supplied continuously by the measuring device 1, is put into memory in the two condensers 4e1 411 This memory storage is made possible by means of the closure of the gates 3a 3a under the action of the clock 12 and by means of the blocking caused by the diodes Sa 5a At this instantaneous position, the polarities defined by the reversing device 9a are as follows:

Negative at the points g f and h, and positive at the Points 2 f2, 2-

At the instantaneous position t t, the reversing device 9a, through an impulse from the clock 12, produces an abrupt change of polarity at g g resulting in identical change at f f which then balances the charges of the condensers 4e1 4a At that instant, the diode Sa Sa being suitably orientated, the condensers complete their charge, which is terminated when the levels of f f are equal to those at g g In view of the previously existing levels a, of the condensers 4:1 4a the starting poin1 of the additional charge will occur exactly at the moment when the polarities f f are equal to the levels at,,, which will result, taking account of the characteristic s10pe 0i charge of the condensers, in a displacement 5, 5, corresponding to zero polarity of the points f f At the instantaneous position 13 the signal a, 0: variable height having been converted to a signal k h of variable duration the reversing device 9a, by the actioi of an impulse from the clock 12, again changes the polari ties and brings back the system into the condition whicl it had before l +7\. At this same instantaneous positior 1 the electronic gates 3:1 311 open and permit appli cation to the condensers 4a,, 451 of new values +1 am 5 71 At the instantaneous position t +l, the electronic gate 3:1 311 close, the signal om+l is put into memory an the process starts again as at the instantaneous position r,

The signals I1 11 thus being defined in duration anpolarity proportionally to the level and the polarity c the voltage stored in memory at the instantaneous pos: tions t,,, are treated in the adding device 8a, from whic they are extracted and applied, after selection by th diodes 11a 11a to the valves 10:1 1061 which contrr through the nozzles 13% 13a the torque impulse to b applied before the instantaneous position t The same operations are repeated at every instantar eous position of switching-over, t t 1, t 2, etc defined by the sequence clock.

Assuming that at the instantaneous position t the $11 is displaced from the axis of symmetry of the satellite "t an angle 6 less than 10, the satellite is stabilized from tl instantaneous position t +2, that is to say after two switcl ing phases.

Generally speaking, the method according to the i: vention thus enables solids in slow rotation about the centres of gravity to be stabilized when it is possible detect the components of the final direction to be givt to the axis of rotation.

FIG. 12 shows diagrammatically the arrangement of the various elements. It is seen in particular that the axes of the discharge nozzles 13a 13a 13b 1312 are directed parallel to the axes Gx, Gy, that the director cosines cc and p can be detected by means of a device comprising a lens 22 mounted with its axis along Gz, which supplies an image 8, of the point 8 on a system 25 ruled in squares and translating, by means of an appropriate means such as a photo-electric device with amplification for example, the real co-ordinates of the said director cosines.

It will of course be understood that the invention has only been described and shown purely by way of explanation and not in any sense by way of limitation, and that modifications of detail may be made thereto in accordance with its spirit, without thereby departing from its scope.

In particular, it is quite obvious that the invention is in no way limited, with regard to its possible applications, to that of the stabilization of an artificial satellite, which has only been given by way of example. In fact, the invention is applicable to all aerial vehicles comprising eventually, and in all possible combinations:

Artificial satellites,

Ballistic devices,

Missiles from the moment at 'which the dilference between the actual direction of these vehicles and the fixed direction can be detected and measured.

Similarly, it is quite clear that, according to the nature of the detector which is employed, the vehicle can be compelled to remain:

Aimed at the sun, a point on the earth, a point in space, etc.

Oriented to follow a line of a magnetic field, a radioelectric field, or a ray of coherent light, etc.

I claim:

1. An aerial vehicle with stabilization means comprising a means for detecting deviations from a predetermined desired flight path,

means for generating electrical signals corresponding to said deviations, said means being connected to said means for detecting deviations,

means to determine optimum rotational positions for application of impulse correction to said vehicle and connected to said means for generating electrical signals including a sequencing means for controlling application of one or a plurality of correctional impulses, as required, to the vehicle at determined rotational positions,

and means for effecting a positional correction of the vehicle, said means being connected to said means to determine optimum rotational positions.

2. The apparatus of claim 1 wherein the stabilization means is further characterized by the time intervals between optimum rotational positions being determined by the stabilization means in accordance with the relationship:

where T is an actual period of rotation of the vehicle and A and C are respectively one of the first two and the third moment of inertia of said vehicle.

3. The apparatus of claim 1 wherein the stabilization means is further characterized by said means for detecting deviations from a predetermined desired fiight path functioning by detecting deviations in a continuous manner by measurement of the director cosines of said desired flight path with respect to a geometric axis of the vehicle, said axis being displaced from said predetermi ed flight path by an angle equal to 1rA/C, in which A is one of the first two moments of inertia of the vehicle and C is the third moment of inertia. 4. The apparatus of claim 1 wherein the stabilization means is further characterized by a plurality of memory devices, said means for generating electrical signals including a sampling device having a first series of electronic elements controlling the storage in memory devices of a signal from said detector at each of the opti mum rotational positions, a second series of electronic elements controlling on the one hand the readout output of said memory-stored indications at each of the optimum rotational positions of switching immediately following that of detection and, on the other hand, after a very short lapse of time, the desensitization of said memory devices. 5. The apparatus of claim 4 wherein the stabilization means is further characterized by said means for generating electrical signals further including two electronic circuits connected in parallel to said means for detecting deviations and controlled by said sequencing means, a and said means for effecting a positional correction including two gas-jet nozzles mounted on an axis of the vehicle. 6. A method of stabilization of an aerial vehicle during roll or spin conditions which comprises detecting deviations of said vehicle from a predetermined desired flight path, generating electrical signals corresponding to said deviations, determining optimum rotational positions of said vehicle for application of impulse correction, and sequentially applying incremental correctional impulses to said vehicle at said optimum rotational positions. 7. The method of stabilization of claim 6, further characterized by the time interval between optimum rotational positions being determined by the relation:

where T is an actual period of rotation of the vehicle and A and C are respectively one of the first two and the third moment of inertia of said vehicle. 8. The method of stabilization of claim 6, further characterized by performing in a continuous manner the steps of detecting subsequently encountered deviations from a predetermined desired flight path by measurement of the director cosines of the desired flight path with respect to a geometric axis of the vehicle. 9. The method of stabilization of claim 8, further characterized by sequentially applying :further incremental correctional impulses to said vehicle at optimum rotational positions.

References Cited UNITED STATES PATENTS 3,139,299 6/1965 Garner et al 244- 3,216,674 11/1965 McLean 244l55 X 3,333,789 8/1967 Schreiner 244-3.l5

VERLIN R. PENDERGRASS, Primary Examiner.

US. Cl. X.R 

